The long term objectives of this proposal are to establish the metabolic pathways of sphingolipids, their control mechanism, and their functional role in developing brain. These lipids include cerebrosides, sulfatides, and gangliosides. Cerebrosides and sulfatides are major constituents of myelin and are specifically localized in this mechanism. Gangliosides are present in plasma membranes of various nerve cells especially neuron and nerve endings. Cerebrosides and sulfatides are believed to contribute to the function of the myelin membranes. The mechanism of myelination, however, remains unclear although lack of myelin or demyelinating conditions always results in severe mental retardation and disruption of nerve function. Gangliosides, on the other hand, may participate in receptor and neurotransmitter functions. In this proposal two aspects of the function of the complex lipids will be addressed: first, do glycosphingolipids contribute to the compaction of the myeline membrane into its characteristic multilayers? Second, how are glycosphingolipids transported from their site of snythesis to the site of incorporation into plasma membranes? Both aspects require the ability to measure and isolate very small quantities of glycosphingolipids in tissue samples. Newly developed methods by use of high performance liquige chromatography will be used for this purpose. Aim 1 is designed to extend and improve the method to measure more complex gangliosides. In Aim 2, the role of sphingolipids in myelin compaction will be studied by determining the affinity between these and other myelin components. A newly acquired immunohistochemical technique will be used with varieties of purified myelin lipids and their radioactively labeled derivatives. Aim 3 is designed to study the role of the cytosol pool of glycosphingolipids in their transport from endoplasmic reticulum or golgi apparatus to the site of myelin assembly, and Aim 4 will investigate the transport of these lipids from neuronal cell bodies to nerve endings and axonal membranes by axonal flow.